Exhaust aftertreatment systems are used to receive and treat exhaust gas generated by IC engines. Conventional exhaust gas aftertreatment systems include any of several different components to reduce the levels of harmful exhaust emissions present in exhaust gas. For example, certain exhaust aftertreatment systems for diesel-powered IC engines include a selective catalytic reduction (SCR) catalyst to convert NOx (NO and NO2 in some fraction) into harmless nitrogen gas (N2) and water vapor (H2O) in the presence of ammonia (NH3).
Generally in such conventional aftertreatment systems, an exhaust reductant (e.g., a diesel exhaust fluid such as urea) is injected into the aftertreatment system to provide a source of ammonia, and mixed with the exhaust gas to partially reduce-the NOx gases. The reduction byproducts of the exhaust gas are then fluidically communicated to a catalyst included in the SCR aftertreatment system to decompose substantially all of the NOx gases into relatively harmless byproducts which are expelled out of such conventional SCR aftertreatment systems.
Engines that use aftertreatment systems for treating the exhaust gas (e.g., diesel exhaust gas) can include bigger engines used in several off-highway applications. These applications include engines that have a volumetric capacity of greater than about 15 liters, which are typically used in on-road trucks. Due to the large amount of exhaust gas emitted by bigger engines, such engines often include aftertreatment systems that include a plurality of SCR systems (e.g., 2, 3, 4 or even more) for treating the exhaust gas. The exhaust gas is generally divided into equal portions such that each portion flows through a single SCR system disposed on a separate fluidic pathway and configured to treat only the portion of the exhaust gas that flows through that SCR system. Sensors for sensing temperature, NOx gases, ammonia, oxygen, etc. are disposed on each aftertreatment system and provide information on operational parameters of each portion of the exhaust gas. This increases the overall size of the aftertreatment systems and increases cost.